The widespread use of digital processing technology has found its way into a variety of equipment and, in some form, into most industries. In many applications involving communication of different types of information, data processing arrangements have been configured to multiplex information from each type of information source over various communication-media types and arrangements.
In a typical multimedia application, for example, one type of data processing arrangement permits several data sources to transmit data over the same communication channel. In this environment, a multiplexing arrangement is typically used to process certain types of data from each of the several data sources and to present this processed data to the communication channel transmission equipment in an orderly fashion. The multiplexing arrangement receives an input from each data source and, through a single output port, provides the data to the communication channel according to a preestablished multiplexing protocol.
A problem arises, however, when attempting to maximize the efficiency and use of such a shared communication channel. The various data sources at the input side of the multiplexer provide data at varying rates based on the particular applications served by the data sources. The data transmission equipment, at the other side of the multiplexer, typically includes a specific maximum data transmission bandwidth that permits the transmission of data up to a certain upper limit. If the preestablished multiplexing protocol effects data collection from each of the data sources according to a specified rate, the multiplexer often fails to process enough data from some data sources. Moreover, the multiplexer often fails to process any data from other data sources. Such data processing failures render approaches of this type unacceptable for many data processing applications.
One approach to dealing with this problem involves using a relatively large stack data register arrangement, such as a first-in-first-out (FIFO) memory circuit, at each of the inputs to the multiplexer and at the output of the multiplexer. Using this arrangement, the multiplexer can draw data from each of the FIFOs at the input side and provide valid data to the FIFO at the output such that the output FIFO always contains data ready for transmission. The data transmission equipment will virtually always be filling its channel bandwidth by constantly drawing valid data from the output FIFO. One drawback of this method is that each FIFO introduces a delay in processing the data from the input source through to the transmission channel.
Another approach to this problem involves implementing one of the input data sources, such as a video encoder, using an internal mechanism that scales its output data rate by adjusting the amount of distortion in the encoded video signal. In approaches of this type, the multiplexer typically attempts to track the available bandwidth according to the amount of data in the output buffer of the video encoder. With the multiplexer drawing data from the FIFO of the video encoder according to available channel bandwidth, the video encoder decreases its data rate when the output buffer level rises and increases its data rate when the output buffer level drops. This approach, however, requires that the video encoder maintain a nominal or quiescent buffer level, thereby introducing undesired and often unacceptable delay. Another drawback to this approach is that the video encoder lacks direct access to the data rates of the other data sources, which together with the characteristics of the transmission determine the available channel bandwidth. Thus, the video encoder has to wait for changes in the data rates of the other data sources to affect the video encoder output buffer level. This delay reduces the speed at which the video encoder can adapt to these changes. Moreover, this approach often results in sudden changes in the output data rate of the video encoder. Sudden changes of this type can cause sudden changes in coding distortion, which adversely affect the perceived video quality.
Accordingly, a need exists for an improved data processing arrangement and method thereof for efficiently transmitting data in a manner that overcomes the above-mentioned shortcomings.